In an optical network, when a route (a path) from a transmission-side node to a reception-side node is designed, parameters associated with the route are measured based on a field investigation performed in advance. The parameters may include, for example, a number of transmission lines between the transmission-side node and the reception-side node, a distance of each transmission line, a transmission loss of each transmission line, and a chromatic dispersion coefficient of each transmission line.
Regarding the measurement of parameters, for example, Japanese Laid-open Patent Publication No. 6-174592 and Japanese Laid-open Patent Publication No. 4-177141 disclose a technique in which a measurement system including an optical fiber with a known length is connected to one branched transmission line of pulsed light and a chromatic dispersion coefficient (for example, 16 ps/km/nm for an SMF (Single Mode Fiber)) is measured based on a change in delay time with a change in wavelength of a pulsed light. It is also known to use an OTDR (Optical Time Domain Reflectmeter) method to measure a length, a transmission loss, and a chromatic dispersion coefficient of an optical fiber in a route based on a reflected light with respect to incident a pulsed light. Parameters obtained as a result of the measurement are used to evaluate a transmission performance of a route in designing the route.
For example, Japanese Laid-open Patent Publication No. 2009-118101 discloses a technique in which a parameter associated with a transmission performance of each of apparatuses located in a route is stored in the apparatus, and a cumulative value of the parameter is transmitted and received sequentially from one apparatus to a next apparatus, and the transmission performance of the line is evaluated in the apparatus located at the end of the line. Japanese Laid-open Patent Publication No. 11-008590 discloses a technique in which parameters associated with the transmission performance of apparatuses in a route are collected, a bit error rate or the like is calculated based on the collected parameters, and the apparatuses are controlled so as to minimize the bit error rate.
Routes in optical networks are becoming more complicated as new optical fibers are added to the networks to meet increasing requirements for communication and as mesh-type networks with many route patterns are introduced. In the case of an optical network of a type of a WDM (Wavelength Division Multiplexing) network including a wavelength division multiplexing apparatus, routes are manages for each wavelength, which results in an increase in complexity of routes. The wavelength division multiplexing apparatus is an apparatus configured to multiplex a plurality of wavelength signals. An example of a wavelength division multiplexing apparatus is an OADM (Optical Add-Drop Multiplexer).
The above-described measurement of parameters is performed for at least all routes being used from a transmission-side node to a reception-side node, which results in an increase in a time and cost to design the network and an increase in management burden. This problem is more significant when the route is dynamically switched to adapt to a time-dependent change in communication traffic, because a change occurs in the route condition.
On the other hand, in a case where the measurement is performed not for all routes but for particular routes, the number of routes to be measured may be reduced. However, even in this case, it takes a long time to measure all transmission lines in each route.